The present invention generally relates to a piezoelectric resonator and more particularly, to an improved strip type or rectangular type piezoelectric resonator for use, for example, in oscillators, electrical filters and the like.
With the recent progress in the field of integrated circuits, inexpensive ceramic resonators have been widely utilized for the actual applications, and normally, disc type or rectangular plate type piezoelectric resonators are generally employed for the purpose in a range of resonance frequencies from 100 KHZ up to 1 MHZ so as to utilize the expansion mode of vibration thereof.
As shown in FIG. 1, the known rectangular plate type piezoelectric resonator referred to above includes, for example, a piezoelectric ceramic substrate 1, main electrode faces 2 and 3 formed on the opposite surfaces of said piezoelectric ceramic substrate 1, and lead wires 4 respectively connected to said main electrode faces 2 and 3. However, in the rectangular plate type piezoelectric resonator as described above or disc type piezoelectric resonator conventionally employed, there have been such disadvantages that they are generally large in size, and moreover, tend to produce spurious waves due to thickness mode vibration based on the fundamental wave.
Meanwhile, as shown in FIG. 2, there has also been conventionally available a strip type piezoelectric resonator utilizing length mode vibration based on the fundamental wave, and having a construction generally similar to that of the rectangular plate type piezoelectric resonator in FIG. 1 as represented by like reference numerals. Although advantageous in that the dimensions are reduced as compared with the rectangular plate type or disc type piezoelectric resonator, the conventional strip type piezoelectric resonator as described above still has disadvantages in that undesirable spurious responses due to width mode vibration and thickness mode vibration tend to be produced.